How big a print can I make from a 640 × 480 image?

Well, the true answer is you can make as big a print as you want but very quickly you will start to see “blocks” (pixelization) and the quality will drop off. To maximize the capability of your printer, you should print a picture a size that the printer can handle. Here we introduce a new term “dots per inch” or “pixels per inch.” For example, you have a 640 × 480 image and you want to print it at 200 dpi (dots or pixels per inch). 640 divided by 200 equals 3.2 and 480 divided by 200 equals 2.4 so if you print this picture at 3.2″ × 2.4″ you will get a print with 200 dots per inch. We recommend 200 dpi as a minimum for good quality prints. Now, let’s work one of these problems backwards. Let’s say we want to print an 8 × 10-inch picture at 300 dpi. What resolution must we have to do this? 300 times 8 is 2400 and 300 times 10 is 3000. So we would need a 3000 × 2400 image to do this. Let’s see, 3000 × 2400 is 7.2 megapixels! That would be one very nice digital camera and one very large file, especially if it wasn’t compressed.